NATIONAL PHD IN HERITAGE SCIENCE

Thesis title: Patrimonio culturale e mucillagini vegetali: l'Opuntia ficus-indica (OFI) nelle pitture murali per il recupero e la valorizzazione dei beni architettonici con approccio ecosostenibile. Il caso studio della Real Villa Favorita ad Ercolano (NA).

The mucilage of Opuntia ficus-indica (OFI) is the focus of this research as a natural biopolymer for the conservation of wall paintings, investigated within a framework that integrates historical knowledge, scientific experimentation, and sustainability. Extracted from cactus cladodes, a residual biomass generated by annual pruning, the mucilage represents a potentially valuable resource in the Italian context, consistent with the principles of circular economy and green conservation. The theoretical and scientific foundation of the study lies in the analysis of pre-Hispanic Mexican painting techniques, in which “nopal” mucilage was employed as an additive and binder to enhance the durability of mural layers, and still empirically used today in building materials. Building on this evidence, the research proposes a critical and scientifically grounded reinterpretation of this traditional technology, supported by advanced diagnostic tools and controlled experimental methodologies. The experimental work is structured around three complementary applications: use as a consolidant for dry wall paintings, as an additive in lime-based formulations, and as a binder for retouching. Tests carried out on specifically designed mock-ups, supported by physico-chemical characterization, thermo-hygrometric aging cycles, bioreceptivity assessment, and non-invasive diagnostic investigations, demonstrated good compatibility with carbonate substrates, chromatic stability, adequate response to simulated degradation cycles, and no increase in microbial proliferation. The results highlight the versatility of the material and its potential integration into planned maintenance strategies. The research findings are applied to the case study of the Real Villa Favorita in Ercolano, Naples, Italy, where a diagnostic campaign on the painted rooms provided the knowledge base necessary to evaluate the future controlled application of the mucilage. Overall, the study contributes to the definition of a conservation model that integrates traditional techniques, scientific innovation, and circular economy principles, promoting the valorization of residual biomass as a sustainable strategy for cultural heritage conservation in the contemporary context.